The present invention relates to a method for the series production of an essentially circular cylindrical outer column for the reception in the interior of a safety steering column for motor vehicles.
It is known that the driver of a motor vehicle during frontal collision of the motor vehicle may suffer considerable injuries because his chest is pushed against the steering wheel. In order to reduce such danger of injury to the driver, it is preferred to construct the steering column as a safety steering column with a substantially circular cylindrical outer column which receives in the interior thereof a steering column which during frontal collision will telescopically collapse.
The steering wheel is fixed to the end of the safety steering column which is directed towards the passenger compartment of the vehicle and the steering linkage is connected to the opposite end of the steering column. The outer column comprises an upper essentially smooth walled protecting tube which is yieldably attached to a fixed portion of the vehicle and a lower corrugated tube coaxially connected with the protecting tube and constructed to collapse under absorbation of energy upon impingement of the chest of the driver onto the steering wheel. The corrugated tube is fixedly connected with another part of the vehicle.
Two circular cylindrical smooth walled tubular blanks are used for the manufacture of the outer column of a safety steering column.
The diameter of an upper region of the tubular blank for the protecting tube is reduced in at least one working station. Eventually this tubular blank is subjected also at its end region to a machining operation for finishing the inner surface thereof and for providing a chamfer at the end and subsequently thereto this tubular blank is fed to an indentation and hole forming station in which it is provided at the upper end region with indentations as well as holes.
The apertures are provided in the first tubular blank to receive a bolt of a steering wheel lock and also for connection of holding means. The holding means preferably comprise a holding bracket welded to the tubular blank. Finally, the first tubular blank for the outer column is widened at the lower end thereof in order to be subsequently pushed onto the corrugated tube.
The blank for the corrugated tube is first fed to a corrugation station in which the tubular blank is formed into a corrugated tube by radially pressing successive corrugations into its wall. Eventually a guide bracket may be fixedly welded to the lower region of the corrugated tube.
Finally, the corrugated tube and the protecting tube are connected at end regions by welding to each other.
The thus-formed outer column for a safety steering column evidently has to satisfy certain quality requirements. During their manufacture certain tolerances have to be maintained regarding the quality of the welds provided as well as the dimensions of the finished products.
It is therefore necessary during the series production of outer columns of safety steering columns to check the parts during their production, respectively, the end product in a plurality of control stations with respect to the required quality and especially with respect of maintaining the predetermined tolerances. If these tolerances are not maintained the faulty part has to be removed from the assembly line.